Case Study. Contract Manufacturer C19 Failure Analysis. CM C19 Failure Analysis 2014 SWC Page!1

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Wilfred Morris
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1 Case Study Contract Manufacturer C19 Failure Analysis CM C19 Failure Analysis 2014 SWC Page!1

2 Contents Introduction Page 2 Document Review Page 3 Process Audit & Test Build Page 4 Root Cause Identification Page 5 CM SCAR Page 6 Conclusion / Next Steps Page 7 Introduction This case study is meant to provide a high level review of activities undertaken during the current new project launch for a client that supplies a high-level assembly and proprietary technology to their end customer, a major medical OEM. The printed circuit board assembly (PCBA) is outsourced with a prominent contract manufacturer (CM) and the situation is that a lifted component at location C19 on the printed circuit board was shipped on the original 400 piece Verification & Validation (V&V) Build. The failed board was not detected during testing at either the CM or the client, but was detected during the full functional test at the OEM. The Client has indicated that the immediate task is to restore confidence with their OEM customer in the capability of both the Client and their PCBA CM supplier to effectively produce this product, and in the client s ability to manage their supplier through recovery from this failure. CM C19 Failure Analysis 2014 SWC Page!2

The approach will include: 1. Determining Defect Root Cause, 2. Determining Test Escape Root Cause, 3. Assessing the CM s Process, 4. Improving the CM s SCAR response to meet ISO 13495 requirements.

3 The approach will include: 1. Determining Defect Root Cause, 2. Determining Test Escape Root Cause, 3. Assessing the CM s Process, 4. Improving the CM s SCAR response to meet ISO requirements. Document Review A thorough review of all Client/CM/OEM reference documents was performed to assess the body of work already completed and to develop a working plan and process audit for the onsite visit with the Client at the contract manufacturer s facility. The documents were grouped into four major categories: 1. APQP Documents 2. V&V Build Documents. 3. Supplier Assessment Documents 4. SCARs APQP Documents Documents reviewed included: Test Data Sets Process Flow pfmea Control Plan IQ / OQ Protocols CM C19 Failure Analysis 2014 SWC Page!3

4 V&V Build Documents Documents reviewed included: V&V Test Data Unit Process Data History OEM PCBA Test Document Client PCBA Specifications Supplier Assessment Documents Documents reviewed included: CM Process Questionnaire Assessment Summary Audit Results Audit Response to the OEM Supplier Management Plan PQ Protocol CM existing SCARs Two existing Client / OEM Audit SCARS One Tombstoned C19 Component SCAR Process Review Audit & Test Build Using input from the Client/CM/OEM reference documents, a process audit was developed to help drive to root cause and verify the capability of the contract manufacturer s PCBA process. The audit included 40 attributes across 5 sections: Raw Printed Circuit Board, Electronic Component, Assembly General, Client part specific Control Plan & pfmea, & the Client PCBA Specification & Audit Corrective CM C19 Failure Analysis 2014 SWC Page!4

5 Action. The audit was conducted while onsite at the CM s facility and published in the file CM Tombstone Process Audit. In addition to performing the process audit, the 400 piece test build was observed with the client. The entire PCBA process was followed as the order was built, including paste application, component placement, AOI, reflow, functional test, inspection, final audit & box audit. The result of the build was 100% yield with zero lifted components. Review of historical internal performance shows the CM s PCBA process to be capable and operating at a 5.5 sigma level. Root Cause Identification The mechanics of tombstoning are a result of the wetting surface forces of molten solder and the mass and geometry of the component termination land. As the flux and solder alloy liquefy and wet to each side of a component, they apply small amounts of torque through surface tension. If the solder paste under one termination melts and starts wetting to the termination before the other side does, the force applied by the wetting action can lift the component up on its end. From a component design standpoint, typically the smaller and lighter CM C19 Failure Analysis 2014 SWC Page!5

6 the component is, the more susceptible it is to tombstoning. Factors related to tombstoning are numerous but can be classified into two main categories: Design Controlled and Process Controlled as detailed in the above diagram. Problem solving tools used: Brainstorming, Fishbone Diagram & Pareto Analysis. The problem solving methodology that was followed was to first identify all potential contributors (40), reduce those to a list of probable contributors (10), and finally identify the top 4 contributors. Through further analysis it was determined that the Root Cause was Placement and tangible actions were taken. A thorough analysis of the process & defect data has shown this to be an anomalous defect with normal variability that could fall within a 99.8% process yield. Any further reduction in escape risk would need to come from detection improvement, not prevention. The immediate action was to refine the AOI program for this part number to improve detection specifically for lifted components; a controlled experiment verified effectiveness of this action. It was discovered that ~20 nonfunctional components (filters) were not being tested during Functional Test; additional detection improvement may be achieved by developing an In Circuit Test and/or X-ray strategy collaboratively with the Client, OEM & CM. The root cause analysis done by the CM was documented in the file CM Root Cause Analysis Client ABCD-XXXXXXXX. CM SCAR After a thorough review of the document and a compare & contrast to the expectations of an ISO CAPA response, it was determined that the initial SCAR submitted by the CM did not identify root cause and was missing a number CM C19 Failure Analysis 2014 SWC Page!6

7 of critical activities and information. A detailed list of recommendations was prepared to guide the CM through the problem solving & documentation that would be required to be included in the revised SCAR This was published in the file CM CAPA Recommendations SWC. The elements of the SCAR identified as needing improvement were Root Cause, Short Term Corrective Action, Permanent Corrective Action, Corrective Action Verification, Preventive Action, Risk Assessment & Effectiveness of CAPA. The resubmitted SCAR meet the expectations of ISO Conclusions / Next Steps The key accomplishments were driving to root cause for the C19 failure and escape, verifying the contract manufacturer s PCBA capability, completing the CM s SCAR, Client and OEM approval and release for the PQ (process qualification) Build. The immediate next step would include guiding the CM s PQ build for approval and production release. Subsequent next steps would include ongoing monitoring of the Client s product through the contract manufacturer s production process to assure all acceptance criteria identified in the PQ Protocol continue to be met. CM C19 Failure Analysis 2014 SWC Page!7

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